    (condp = energy-unit
      :ft-lb [:ft-lb (tuc/draw-normal 4.340741e10 1.443922e10)]
      :J     [:J (tuc/draw-normal 14670.972535 5275.739520)])))
+
+(defn typical-force
+  ([] (typical-force (rand-force-unit)))
+  ([force-unit]
+   ;; Retrieved from http://www.excoresources.com/appalachia/ and
+   ;; https://en.wikipedia.org/wiki/Casing_string on 28-Dec-2020.
+   (let [typical-casing-outer-diameter-inches (+ 5 (/ 1 2))
+         typical-casing-pipe-witdth-inches    0.545
+         typical-casing-inner-diameter-inches (- typical-casing-outer-diameter-inches
+                                                 typical-casing-pipe-witdth-inches)
+         typical-casing-area-sq-inches        (* 2 Math/PI (/ typical-casing-inner-diameter-inches 2))
+         typical-pressure-psi                 (typical-surface-treating-pressure :psi)
+         typical-force-lbf                    (* typical-pressure-psi typical-casing-area-sq-inches)]
+     (condp = force-unit
+       :lbf [typical-force-lbf force-unit]
+       :N   [((convert-units-f :lbf :N) typical-force-lbf) force-unit]))))

(defn convert-units-f [from to]
  (let [factors   {[:lb-per-cu-ft :kg-per-m3] 16.0185
                   [:ft-lb :J]                1.35582
                   [:m :ft]                   3.28084
                   [:kg :lb]                  2.20462262185
                   [:psi :kPa]                6.894757293168361

                   [:kg-per-m3 :lb-per-cu-ft] #(/ % (factors [:lb-per-cu-ft :kg-per-m3]))
                   [:ft-lb :J]                #(* % (factors [:ft-lb :J]))
                   [:J :ft-lb]                #(/ % (factors [:ft-lb :J]))
                   [:lbf :N]                  #(* % (factors [:lbf :N]))
                   [:N :lbf]                  #(/ % (factors [:lbf :N]))
                   [:ft :m]                   #(/ % (factors [:m :ft]))
                   [:m :ft]                   #(* % (factors [:m :ft]))
                   [:lb :kg]                  #(/ % (factors [:kg :lb]))
